Diamond has the advantages of high melting point, low compressibility coefficient, high symmetry and high refractive index. It has wide applications in industrial manufacture and scientific research. Owing to the specific properties and uses thereof, quite long ago, people tried to prepare it by chemical method in order to supplement the insufficiency of the natural storage. A large amount of time and a long course of events have been spent on solving a series of problems such as the exploration of transition condition and relevant facilities as well as searches for an effective catalyst. In 1954, first work on successful preparation of diamond by conversion of graphite under strict control of high temperature and high pressure with FeS used as the flux was reported in Nature, Vol. 176, 51. Thereafter research and production of man-made diamond have been developing rapidly and grows to be a new industry. The conventional method of preparation for diamond involves the use of graphite as the raw material, molten metals (Ni, Cr, Mn, Fe, Co, Ti, Al etc) as the catalyst and flux, little diamond particles as crystal seeds. Thus graphite is converted into diamond under pressure of 5-100 kbar and high temperature of 1200-2400K. This kind of method has to endure critical conditions and very high cost.
Chinese patent 97119450.5 and Science, 1998, Vol. 281, 246 disclosed a method in which CCl4 was used as the carbon source, Na was used as the reducing agent and solvent, Ni—Co metal was used as the catalyst. CCl4 could be converted into diamond at 700° C. The size of the diamond particles thus prepared was less than 0.2 micrometer and the method had the danger of explosion. Therefore at the moment, the method is not suitable for large-scale industrial production of diamond.
On the other side, the global storage of CO2 on earth is extremely abundant. CO2 is also the by-product of exhaust emission of many industrial manufactures. When CO2 is expelled into air, “greenhouse effect” will be induced which will cause the global weather getting warmer. As a result, many countries in the world have to spend huge amount of manpower and resources to bring it under control. CO2 is non-toxic and cheap. Utilization of CO2 as main raw material for synthesizing inorganic and organic compounds is one of the objectives of chemists. It is regrettable to notice that up to now no any well-industrialized method of treatment that uses CO2 as raw material in huge amount has been reported.